On Friday, a bill opening marriage and adoption to same-sex couples passed the French Senate, following a week of intense, often acrimonious debate. “We simply acknowledge full citizenship for gay couples,” said Christine Taubira, the French Minister of Justice, following completion of the controversial vote. The Bill will now return to the National Assembly, which has already approved the proposition, for a second reading, followed by a final reading in the upper house.

According to Federico Grana, the leader of a gay rights group that drafted the proposal, the vote represented “an historic moment” for Uruguay, a country that becomes the third across the American continent, following Canada and, more surprisingly, the deeply Catholic Argentina, to recognise equality in marriage.

Before this week, eleven countries had already passed legislation to allow same-sex marriage, with 10 other states, including Britain and Ireland, currently in the process of pushing through bills.

Although change may appear to be happening at pace, the campaign for gay rights is decades old, with incremental steps leading back to the sixties responsible for the swathe of parliamentary successes currently being celebrated by advocates around the globe.

As human rights campaigner Peter Tatchell told The Huffington Post UK: “Marriage equality is an idea whose time has come. It’s an unstoppable global trend.” It’s a sentiment BJ Epstein, a lecturer at the University of East Anglia who specialises in queer literature, agrees with.

“Governments are starting to look quite ridiculous not giving equal rights to all people and all relationships,” she tells The Huffington Post UK. “In a few years people are going to wonder why it took such a long time.”

But why has it taken such a long time for governments to recognise such a basic principle as equality in marriage for same-sex couples? For Stanislas Kraland, a journalist for the Le Huffington Post who has reported extensively on the gay marriage debate in France, the answer is both generational and political.

“The answer stems from an analysis of who is against gay marriage in France,” he said. “It’s the elderly, right-wingers (because gay marriage is a left wing project) and the majority of Catholics. That’s a lot of potential voters.”

The Netherlands became the first country to pass gay marriage legislation in 2001, which Kraland argues, in sociological terms, is only very recent, while the push for equality in this area only started in France in the 1990s.

“During the 1970s, French homosexuals were against the idea of marriage per se,” he said, however, once equality became an issue for the French homosexual community in the Nineties, the law moved relatively quickly, making civil unions legal in 1999, and same-sex marriage legal this year.

In Britain, civil partnerships were made legal in 2004, while the current gay marriage Bill wrestled its way through the House of Commons in February, and is due to be debated in the House of Lords later this year. Following amendments, the Bill should be handed back to the Commons, with political commentators expecting it to be signed into law by the end of the year.

Unlike many of the countries that have already passed legislation, most notably Spain and Argentina, Britain isn’t saddled with a strong religious voice to offer sustained opposition. Yet, rather than pioneer gay marriage, as some might expect from such a secular society, the UK has lagged behind Belgium, Canada, Denmark, Sweden, Norway and even South Africa.

“People are becoming less religious which helps,” said Epstein, “but in many ways the UK is a rather conservative country. As a foreigner living in the UK (she’s originally from Chicago), Epstein admitted she has been surprised at just how conservative the British are. “If you go to places like London and Manchester it’s very diverse, but go to a small city or town and it’s not diverse at all. People are scared of otherness.”

Still, the lecturer believes the world has reached a tipping point on gay marriage. “Some countries are going to take a long time, but I think we’ve got there and it is just a matter for the other countries to catch up.”

So with much of Europe adopting or having adopted equality for same-sex couples, campaigners are now looking towards the next major battle, the USA. Still, for Epstein there’s plenty of optimism.

“Even conservative religious people in the US are beginning to see that they have no choice but to go along with it,” she said.

Since Obama’s re-election last year, arguably a watershed moment for the GOP, which was plagued throughout the campaign by outspoken representatives offering a series of public faux pas on social issues, a number of politicians have “evolved” their thinking on the issue of gay marriage.

At the time of publication of this article, 14 Senators – 13 Democrats and one Republican – had publically changed their views in favour of accepting gay marriage in the past month alone, along with former secretary of state Hillary Clinton.

For Noah Michelson, the Editor of Huff Post Gay Voices in the US, the post-election change has been driven by two factors. “It’s both people truly evolving with their thinking, but also not wanting to be seen as having fallen on the wrong side of history,” he said.

“I don’t think we can discount that, as it gets easier for people to come out of the closet, more people than ever know someone who is LGBT… and these personal relationships really can transform the way someone (re) considers equal rights.”

Last year’s election also brought into focus the political necessity for change on this issue. “Many politicians are realising that marriage equality is heading our way whether they like it or not and if they don’t come out in favour of it, they’re going to look foolish – and it could even cost them their positions,” said Michelson.

For Epstein, it’s a matter of urgency that the US adopts equality in marriage. “Many countries look to the US, and for a country that’s so religious and so conservative to say ‘yes, we accept gay marriage’, it would be a huge boost for the cause. Other countries would take note.”

And there’s the rub: America remains a country deeply enthralled by God and, unlike many other countries in the first world, America’s brand of religion is not only political but has a very loud voice.

“Religious opposition to gay marriage is still a huge issue in the US,” said Michelson, “but not necessarily because the majority of people actually believe that marriage equality is antithetical to believing in the Bible, but because the far Right and Evangelical movement is so vocal and has worked so tirelessly to ensure that their message is heard.”

Still, the Defence Of Marriage Act (DOMA) is currently under review, with the Supreme Court due to decide in June whether it should be overturned, paving the way for states where gay marriage is legal to be afforded federal marriage rights.

Yet the grand prize – national legalisation – remains obscure. As Michelson said: “I do not think we will see gay marriage legalised on a national level any time soon… if ever. It’s frustrating to have gay marriage be decided on a state by state level because in my view, we’re talking about basic civil and equal rights.”

Casting the current fight for equality as a civil right places the campaign in a broader context, one that perhaps mirrors the civil rights movement of the sixties. The importance of the first decade of the 21st century as a social revolution is a question for future sociologists to debate, yet for Epstein, there’s little doubt: “It hard to predict the future, but I think it will be viewed as a moment of change, similar to the way we look back on civil rights or giving women the right to vote.”

As a note of caution, though the trend in the first world is seemingly heading in the right direction, many countries around the world, particularly in Africa and Eastern Europe, appear to be going the opposite way.

This week, a human rights activist was granted bail in Zambia after being arrested for calling for gay relationships to be decriminalised on live TV, while in January, Russian lawmakers passed a bill making gay public events and the dissemination of information about the LGBT community to children punishable by a fine of up to $16,000. In the Muslim world, basic human rights for LGBT individuals is a battle yet to be won.

Still, Tatchell remains certain on the course of history: “The ban on same-sex marriage will eventually go the way of the ban on inter-racial marriage. In a democratic society, everyone should be equal before the law. Most people accept that, which is why the ban will sooner or later be history.”